Tension for sewing-machines



(No Model.)

D. L. KEELER.

TENSION FOR SEWING MACHINES.

No. 255,634. Patented Mar. 28,1882.

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UNITED STATES PATENT OFFICE.

DAVID L. KEELER, OF GRAND RAPIDS, MICHIGAN.

TENSION FOR SEWING-MACHINES.

SPECIFICATION forming part of Letters Patent No. 255,634, dated March28, 1882.

Application filed July 11, 1881. (No model.)

To all whom it may concern:

Be it known that I, DAVID L. KEELER, of Grand Rapids, county of Kent,State of Michigan, have invented a new and useful Improvement inTensions for Sewing-Machines; and I declare the following to be a full,clear, and exact description of the same, such as will enable othersskilled in the art to which it pertains to make and use it, referencebeing had to the accompanying drawings, which form a part of thisspecification.

The object of my invention is to provide a simple and reliablecombination and arrangement of devices by which the needle-thread may begiven a proper tension and be relieved therefrom at the moment of thecompletion of a stitch, so that the stitch will not be drawn beyond aproper point in the fabric, and that thread for a new stitch may bedrawn freely from the spool.

In the drawings, Figure 1 is a view of the interior of a sewing-machinehead, the position of the driving-crank beingindicated by dotted lines.Fig. 2 is an enlarged view of the tension-regulating devices.

A is the case of the sewing-machine head. B is a pressure foot bar; B,its prcs'ser-foot; G, the needle-bar; D, the needle-cam; E, thedriving-head on the end of the driving-shaft. F is a spring-plate, thetension of which is regulated by a set-screw, F. F is an arm projectingdown in the interior of the case contiguous to the periphery of thedrivinghead E. This periphery is not concentric with the shaft, but isslightly bulged at 0, so that when the stitch is formed in the center ofthe fabric this swelled portion shall ride beneath the arm F and in sodoing will press it slightly and lift slightly the spring-plate F above.

The operation of the device is as follows: The thread from the spool ispassed beneath the plate F, and its general tension is regulated by thesetscrew F. At the instant, however, that the stitch is formed in thecenter of the fabric the pressure upon the arm F, as above explained,releases the thread, so that at that instant the thread will draw freelyfrom the spool to form another loop. This prevents the liability ofbreaking the thread at the instant that it is drawn into the center ofthe fabric. Moreover, it prevents the thread from drawing through thefabric, which might be the case were the tension upon the thread uniformand a little too great. I have found the deviceto constitute a veryefiective tension.

I am aware that thread-clamps have been operated to release the threadby cams on rotary shafts and intermediate pins and other connections,and I do not claim such construction broadly.

What I claim is- In a tension device, the combination of thespring-plate F, secured at one end upon the top of the machine-head, thearm I, projecting downward from said springplate, and the disk E,fixedupon the driving-shaft,connected by a wrist-pin and cam-plate with theneedlebar, and having the bulge or cum 0 upon its periphery arranged toforce arm F upward, and thereby lift the spring-plate to release thethread, substantially as described.

In testimony whereof I sign this specification in the presence of twowitnesses.

DAVID L. KEELER.

Witnesses:

WM. WOODWARD, ALFRED D. RATHBONE.

